class Employee:
    _ID = 0
    name = ""
    age = 0
    def __init__ (self,name,age):
        self.name = name
        self.age = age
        self.id = self._ID
        self.__class__._ID += 1
 
    def sayHello(self):
        print("hello {}".format(self.name))
 

em = Employee("Mr.Xie",20)
print(em.name)
print(em._ID)
print("一共实例化了{}个实例".format(Employee._ID))
